In existing medical practice, percutaneous catheters are used for intravenous drug therapy. Problems associated with such systems, which multiply when used on a repetitive basis, include substantial sterile dressing care requirements for patients, increased rate of transcutaneous infection, and venous thrombosis. Without a venous access device, there exists significant risk of the development of thrombosis, venous sclerosis, or destruction of smaller peripheral vessels from repeated vein punctures.
Known subcutaneous venous access devices or ports provide numerous advantages for repeated or sustained injection therapy, in comparison to percutaneous catheters. Such ports are surgically installed under the patient's skin for intermittent or continuous intravenous injections, and are often the method of choice for sustained intravenous treatments. However, known needle-port systems have limitations when a treatment regimen includes the use of toxic chemotherapeutic agents, because of the significant potential for needle displacement from the port's protective, self-sealing silicon septum.
Port-needle displacement is hazardous and typically results in subcutaneous diffusion of injected toxic chemicals, causing necrosis of nearby tissues. Needle displacement may also result in poor deployment of the chemical treatment, in addition to causing physical and emotional discomfort to the patient. Necrosis of tissue typically requires corrective surgery, including debridement of the necrotic tissue, removal of the port, and often skin grafting to facilitate healing. Existing subcutaneous venous access ports thus may increase the potential for infections due to needle displacement and toxic chemical infusions, which is particularly hazardous for malnourished or neutropenic patients or patients with suppressed immune systems.
Another potential problem associated with presently available drug infusion devices is associated with the occurrence of thrombosis, which may require a chemical cleaning treatment, or even premature surgical removal for remedial purposes.
A variety of known ports are described in references, such as U.S. Pat. No. 4,861,341, to address needle displacement, however, none adequately controls the problem. For instance, one configuration disclosed in that patent shows a needle core, or stylet, that creates an expansion section that expands upon removal of the stylet. A second embodiment employs a balloon segment of the needle that is manually inflated after placing the needle in the fluid reservoir chamber of the port. Other embodiments provide permanent, multi-ridged surfaces that cooperate with the septum to secure the needle. None of those or other known techniques for securing the needle in the port operate satisfactorily to secure the needle well, and thus are presently not widely used in medical practice.